This invention relates to an electronic device structure having an electronic component and a circuit board on which the electronic component is mounted, and more particularly, relates to an electronic device structure having an electromagnetic shielding for shielding input/output terminals of an electronic component mounted on a circuit board from electromagnetic waves coming from the outside.
Generally, an electronic device such as an IC chip or an LSI chip is packaged in a PGA (Pin Grid Array) package or a BGA (Ball Grid Array) package having a plurality of input/output terminals (i.e. pins or balls) to form an electronic component. The electronic component is mounted on a circuit board and electrically connected to a printed circuit formed on the circuit board.
It is well known that the electronic device is influenced by electromagnetic waves coming from the outside. That is, there is a case where the electronic device malfunctions when it receives the electromagnetic waves. So the PGA or BGA package is covered with a metal case of film as an electromagnetic shielding to shield the electronic device from the electromagnetic waves coming from the outside.
However, the input/output terminals are still exposed and inevitably receive the electromagnetic waves coming from the outside. Accordingly, there is a case where malfunction (or faulty operation) is made in the electronic device by the electromagnetic waves received with the input/output terminals though the metal film covers the electronic device.
Moreover, the exposed input/output terminals radiate other electromagnetic waves caused by an operation of the electronic device. Consequently, there is a case where other electronic device located near the electronic component faultily operates when the it receives the electromagnetic waves radiated from the input/output terminals.
It is therefore an object this invention to provide an electronic device structure which is capable of preventing input/output terminals of an electronic component mounted on a circuit board from receiving electromagnetic waves coming from the outside.
It is another object of this invention to provide an electronic device structure which is capable of preventing input/output terminals of an electronic component mounted on a circuit board from radiating electromagnetic waves caused by an operation of the electronic component.
It is still another object of this invention to provide an electronic device structure which is capable of preventing an electronic component mounted on a circuit board from malfunctioning.
It is farther still another object of this invention to provide an electronic device structure which does not radiate electromagnetic waves.
Other object of this invention will become clear as the description proceeds.
According to the gist of this invention, an electronic device structure comprises a circuit board having a printed circuit. An electronic component has a body and an input/output terminal projected from the body and mounted on the circuit board by connecting the input/output terminal to the printed circuit. A first electromagnetic shielding is formed on the circuit board for enclosing the input/output terminal when the electronic component is mounted on the circuit board.
In the electronic device structure, the body is covered with a second electromagnetic shielding. The first electromagnetic shielding is located between the circuit board and the body mounted on the circuit board or partially encloses the body mounted on the circuit board. The first electromagnetic shielding has a square frame shape. The first electromagnetic shielding is made of conductive paste such as solder paste by a screen printing method.